Many different methods are known in the area of the automatic control of vehicles. In this respect, reference is made to the attached list concerning the state of the art, which forms an integral part of the present document.
A consideration of the technical development in this field shows that processes or devices which make use of stationary guide structures to control the vehicle have been known for a long time. The simplest guide structures are rails: The vehicle is connected mechanically to the rails and is guided by them. It is also known from, for example, W. German Pat. No. 2,445,001, W. German Pat. No. 2,722,222, and W. German Offenlegungsschrift No. 3,134,749, that "rails" in a general sense can be provided as permanent guide structures, and the vehicle can be effectively linked to them by optical or electrical means, such as by induction, so that it can be guided by them. W. German Offenlegungsschrift No. 3,113,086 also describes a similar method, in which reflective surfaces are provided as stationary guide structures. The position of the vehicle at any point in time is determined opto-electronically with respect to these reflective surfaces, and the vehicle is guided by means of these reflective surfaces, serving here as guide structures, to which the vehicle is optically linked.
W. German Offenlegungsschrift No. 2,704,852 describes a similar method, in which electromagnetic transmitters are used as guide structures, which are linked electromagnetically to corresponding receivers provided on the vehicle, the vehicle thus being guided by these transmitters.
All these methods based on the installation of stationary guide structures suffer from one or more of the following disadvantages:
It is extremely expensive to install a system of guide structures over an area of ground. Severe limitations are thus imposed on the flexibility with which such processes or devices can be used on unprepared ground.
If guide structures are installed permanently at relatively great distances from each other over the area, which means that the vehicle can monitor its position in the area only at relatively long time intervals, it is necessary either to accept considerable deviations between the path desired and the path actually traveled by the vehicle during the time between the vehicle checkpoints or to provide expensive measures on the vehicle which make it possible to orient the vehicle in a relative manner between the checkpoints on the basis of the recordings made of drive and/or steering element activity on the vehicle. Such relative orientation is imprecise, however, because of the unavoidable slippage between the elements mentioned and the ground and must always be verified at the checkpoints indicated.
If, for example, transmitters are provided as stationary guide structures, it is necessary to pay for installing these devices and for laying their electrical cables, but very careful planning is also needed to take advantage of the direct lines of sight available for sending and receiving.
In the effort to make the automatic control of the type indicated independent of the layout of the ground area and thus to avoid the problems involved in installing stationary guide structures and in making precise plans, high-speed electro-optic image-processing methods have been used, as is known from W. German Pat. No. 2,364,002, for example, according to which the vehicle orients itself on the basis of an "image" of the space by comparing instantaneously recorded image information with the nominal image information stored in its memory.
It is now obvious that the concept of using stationary guide structures makes accurate vehicle guidance possible only as long as the effective link between the vehicle and the guide structure is present. The longer this link remains intact or can remain intact, the simpler will be the equipment needed on the vehicle itself to guide the vehicle with some acceptable degree of precision along the intended path during the phases in which the vehicle is no longer linked with the guide structures and thus necessarily wanders off course to some extent as a result of the slippage mentioned earlier.